Magnetic pulse spot welding of bimetals

Review of Aluminum-To-Steel Welding Technologies for Car-Body Applications

“…Recent developments have revealed the possibility of flat sheet lap welding using the outer field of a flat coil on the flyer sheet side and a rigid backing on the parent sheet side. In particular, Aizawa [70,71], Watanabe et al [72], and Manogaran et al [73] have shown that seam lap welding and spot lap welding of metal sheets are also possible. Several multi-material joint combinations that are relevant for the automotive industry have been successfully joined using magnetic pulse welding.…”

“…For example, Aizawa [70] found that without a gap, pre-cleaned surfaces and twice the electrical energy was needed. Manogaran et al [73] proposed to pre-form the parts to-be-welded so that there is a gap between them, in order to avoid the need for costly positioning equipment or spacers between the two sheets.…”

End Closure Joining of Ferritic-Martensitic and Oxide-Dispersion Strengthened Steel Cladding Tubes by Magnetic Pulse Welding

“…First, the taper angle was important to generate a ''jetting'' at the collision point, where the surface oxide layer on the metal workpieces is believed to be ejected and cleaned away by the collision jetting, and the metallurgical bonding is accomplished along the two atomically clean surfaces by the simultaneous impact pressure. [18] At the taper angle of 3 deg, desirable joining was not achieved as noticed from the joints 'A' and 'B' in Figure 4. For joint 'A', no evidence of even localized bonding was found, and the tube was only contacted closely with the end plug.…”

“…[17] The wavy morphology of the bonded interface is generally regarded as a joint formation criterion for the impact welding and the wave formation is strongly attributed to the surface jetting. [10,12,18] From the experimental observation, it was supposed that the process parameters used for sample ''D'' in Figure 4 were well within the ''joinability window'', which describes the optimal collision angle and velocity range to induce the jetting and bonding. For samples ''A'' and ''B'', on the contrary, the collision angle (3 deg) and the resultant velocity were not sufficient to generate the bonding, and thus the whole electromagnetic pressure transferred by the flyer tube was applied as only an impact stress at the collision moment, eventually causing the destruction of the end plug, as shown in Figure 4.…”

“…This observation supports the theoretical aspect of MPW in which the two surfaces to be joined are initially cleaned and activated by collision jetting, and atomistic bonding is then achieved because the impact pressure is acted simultaneously on the clean surfaces in contact with each other. [18] A noticeable microstructural change in the vicinity of the bonding interface was the grain refinement in the 9Cr-ODS steel tube side, as shown in Figure 9. In the MPW process, the flyer tube underwent a high strain rate deformation over a very short period of time (10 to 20 ls), which is similar to various severe plastic deformation (SPD) processes.…”